The present invention relates generally to the field of combustion engines. More specifically the present invention relates to mufflers and secondary air injection systems for combustion engines.
Combustion engines are typically equipped with mufflers to control noise emissions. The muffler on a small engine may be attached directly to the exhaust outlet of the cylinder block or cylinder head, and includes a resonating chamber or chambers designed to dissipate sound. In a typical multiple-chambered, tube-outlet muffler for a small combustion engine, exhaust gases and noise enter the muffler through an inlet conduit attached to the cylinder block. The noise is directed into a resonating chamber. The chamber walls are formed from the muffler housing and may include one or more internal separators or baffles. Exhaust gases and noise pass around or through openings in the separators into other chambers of the muffler, and the noise is dissipated. Exhaust gases exit the muffler through an outlet tube (e.g., exhaust pipe) or a perforate outlet formed from a series of small openings in the muffler housing.
Other than noise emissions, combustion engines typically produce pollutants in their exhaust, which include hydrocarbon emissions, nitric oxide, carbon dioxide, carbon monoxide, and/or other pollutants. The pollutants are formed from unspent fuel and byproducts of combustion carried by the exhaust gases. To mitigate such pollutants, some engines include secondary air injection systems, which introduce fresh air into an exhaust stream while the exhaust gases are still hot from combustion processes. As unspent fuel exits the combustion chamber, the unspent fuel is exposed to oxygen in the fresh air, allowing the unspent fuel to combust or oxidize, essentially cleaning the exhaust gases.